US4856851A - Relay and booster valves for air brake systems - Google Patents
Relay and booster valves for air brake systems Download PDFInfo
- Publication number
- US4856851A US4856851A US07/058,406 US5840687A US4856851A US 4856851 A US4856851 A US 4856851A US 5840687 A US5840687 A US 5840687A US 4856851 A US4856851 A US 4856851A
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- United States
- Prior art keywords
- pressure
- piston
- port
- spool
- valve
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- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
- B60T13/00—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems
- B60T13/10—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems with fluid assistance, drive, or release
- B60T13/24—Transmitting braking action from initiating means to ultimate brake actuator with power assistance or drive; Brake systems incorporating such transmitting means, e.g. air-pressure brake systems with fluid assistance, drive, or release the fluid being gaseous
- B60T13/26—Compressed-air systems
- B60T13/261—Compressed-air systems systems with both indirect application and application by springs or weights and released by compressed air
- B60T13/265—Compressed-air systems systems with both indirect application and application by springs or weights and released by compressed air dependent systems, e.g. trailer systems
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
- B60T15/00—Construction arrangement, or operation of valves incorporated in power brake systems and not covered by groups B60T11/00 or B60T13/00
- B60T15/02—Application and release valves
- B60T15/18—Triple or other relay valves which allow step-wise application or release and which are actuated by brake-pipe pressure variation to connect brake cylinders or equivalent to compressed air or vacuum source or atmosphere
Definitions
- the relay valve of modern tractor-trailer combinations constitutes an important part of the air brake system. It is connected to the control line from the operator, to a reservoir constituting the source of operating pressure for the service brake, and to the service brake as well as providing discharge of released brake pressure to atmosphere.
- the operating response, the reliability and the pressure drop through the relay valve are all of critical importance to the brake system as a whole.
- relay valves and booster valves Faced with the state of the art we sought to improve relay valves and booster valves in order to give them a response characteristic in which the relay valve begins operation at as low as one psi of control line pressure as opposed to a few psi minimum control line pressure, heretofore.
- booster valve designed for use in multiple trailer installation which employed basically the same structure as the relay valve with only minimum changes and which provide a significantly faster operation than booster valves in the past.
- booster valve design which reach an operating pressure level of sixty psi in less time than prior booster valves.
- the relay valve employs a body preferably of metal defining a central exhaust port and a pair of delivery ports on the bottom of the valve body as well as a supply port on the side thereof.
- the body defines a cylinder in which a spool or shuttle moves toward and away from the exhaust port.
- a cover seals the upper open end of the body and defines a second cylinder in which a large piston moves from an upward, non operative position to a lower, operated position in engagement with the spool.
- the cover includes control line port through which control pressure is applied to the valve.
- Service brake delivery pressure for the brake system is available at the supply port of the relay valve and sealed from the two or more delivery ports by a pair of O rings sealing the spool or shuttle in the body.
- the spool is displaced downward by the piston and opens communication between the supply port and its pressure surrounding the spool or shuttle and the delivery port by grooves in the intermediate section of the spool cylinder.
- the booster valve in accordance with this invention includes each of the elements of the relay valve described above except that it includes a separator plate located between the valve body and the cover including a bypass check valve between the delivery port and the delivery pressure manifold located beneath the area between the supply inlet line and the delivery port and a second check valve between the delivery pressure manifold and the underside of the piston.
- the booster valve provides virtually 1:1 response at a rear trailer and faster operate and release cycles than heretofore possible.
- FIG. 1 is a pneumatic piping diagram showing a typical single axle trailer service brake system incorporating this invention
- FIG. 2 is a vertical sectional view through the relay valve of this invention employed in the system of FIG. 1 showing the piston 74 partially retracted and the spool 51 is its uppermost position;
- FIG. 2A is a vertical sectional view similar to FIG. 2 with the piston 74 and the spool 51 lowered.
- FIG. 2B is a fragmentary horizontal sectional view of the spool cylinder of FIG. 2;
- FIG. 3 is a graphical representation of the pressure response characteristic of the relay valve of FIG. 2;
- FIG. 4 is a pneumatic piping diagram of a single axle dolly system corporating the booster relay valve of this invention
- FIG. 5 is a vertical sectional view through the booster relay valve of this invention.
- FIG. 6 is a pressure response diagram of the valve of FIG. 5;
- FIG. 7 is a graphical representation of the operate time response characteristic of a conventional brake system
- FIG. 8 is a graphical representation of the operate time response characteristic of a system employing a booster valve of this invention.
- FIG. 9 is a graphical representation of the release time response characteristics of a conventional brake system.
- FIG. 10 is a graphical representation of the characteristic curve similar to FIG. 9 for the booster valve of this invention.
- FIG. 1 a typical single axle trailer brake system is illustrated including a control line 10 and coupling 11 from the tractor cab through which modulated control pressures from the operator are applied by suitable piping and coupling 11.
- Control pressure ranging is supplied through branch lines 12 and 13 to respectively to a ratio relay valve 14 and to a relay valve 15 of this invention.
- Control pressure is also available from line 10 by a quick release valve 16, shut off cock 17 and coupling 20 to any following trailers in use.
- Supply pressure from the tractor mounted compressor arrives over coupling 21, passes through line filter 22 to the main supply pressure line 23.
- Supply pressure is supplied over branch line 24 to the ratio relay valve 14 and therethrough to reservoirs 25 and 26 over lines 30 and 31, respectively.
- the reservoirs 25 and 26 provide on board supply of compressed air which are used;
- the ratio relay valve 14 is preferably a Sealco model 11071 ratio relay valve.
- the relay valve 15 includes a valve body generally designated 40 defining a supply port 41 and a pair of delivery ports 42 and 43 as well as an exhaust port 44.
- the exhaust port 44 includes a cap 45 and a perforated diaphragm 46 both held in place on the underside of the body 40 by machine bolt 50.
- the supply 41 and delivery ports 42 and 43 are tapped for threaded connection through their appropriate supply line 36 of FIG. 1 and delivery line 35 of also of FIG. 1.
- the exhaust port 44 is open to the atmosphere and to the inside of a movable spool 51 which, with its sleeve extension 57, slides in a cylinder 52 in the valve body 40.
- a return spring 53 bears against the exhaust port cap 45 of FIG. 2 and the ends of a number of internal ribs 54 of the spool 51.
- spool 51 The outer surface of spool 51 is sealed toward its lower end to the cylinder wall 52 of the body 40 by an O ring 55 and at its upper end by an O ring 56. Upward movement of the spool 51 is limited by its retaining ring 60 which engages a washer 61 captured in an annular groove in the body 40 by the exhaust port cover 45.
- the spool 51 has approximately one quarter inch of travel.
- the open upper end of the body 40 is closed by cover 70 and is secured in the body by machine bolts 71, one of which appears in FIG. 2.
- the cover 70 includes control line inlet port 72 and defines cylinder 73 in which a piston 74, coaxial with the spool 51, moves in a vertical direction downward in response to control pressure applied to the upper face thereof and upward responsive to the return spring 53 acting through the spool 51 the upper sleeve extension 57 which engages the underside of the piston 74.
- the piston 74 includes a hollow stem 78 sealed to the cap 70 by O ring 84 and having its lower end engaging the sleeve extension 57 of spool 51.
- the sleeve extension 57 of spool 51 includes a plurality of first internal ports which, in the position in which the parts are shown in FIG. 2 are closed by the rim 77 on the downwardly extending end of stem 79 of the piston 74, but which are opened whenever the piston 74 is retracted upward while the sleeve 51 is restrained by its stop 61. Ports 58 allow exhausting of delivery port 42 and 43 pressure to atmosphere through the exhaust port 44 whenever the piston 74 is fully retracted.
- Grooves 66 in the cylinder wall 52 form a port between the cavity open to the supply port 41 and the cavity open to the delivery ports 42 and 43 underlying piston 74.
- This port is closed when the spool 51 is in the uppermost position, as shown in FIG. 2, but is valved open to a greater or lessor extent as spool 51 is caused to move downwardly beyond the position in which it is shown in FIG. 2A, permitting air to pass from supply port 41 to the cavity underlying piston 74 and out of the delivery ports 42 and 43, along the lines including plus marks in FIG. 2A.
- O ring 84 of FIG. 2 is not used but O ring 161 has been added which produces a sealed area of 0.3712 sq. in. identical with the area sealed by O ring 68.
- the relay valve 15 of FIG. 2 when located in the system of type shown in FIG. 1 operates in the following manner:
- supply pressure in the order of 100 to 120 psi is present at the inlet port 41 and fills that port as well as the region surrounding the spool 51.
- This volume is indicated by the presence of (+) signs in the drawing.
- the volume within the spool and within the center void of the piston 74 and the volume above the piston 74 within the cap 70 is at atmospheric pressure as indicated in the drawing by a (-) sign.
- Minus sign is used for convenience but does not indicate negative pressure but merely the lowest pressure in the system.
- the control port 72 and the region above the piston 74 within the cover 70 are at the control pressure which is normally atmospheric pressure with the brake unactuated. This condition is indicated by the presence of circles in the drawings.
- the delivery port 42 and 43 as well as the volume below the piston 74 are all at atmospheric pressure when the brake is not operated and at delivery pressure, for example 1-100 psi when the piston 74 has moved downward sufficiently to engage the spool 51 and displace it downward sufficiently that supply pressure is applied to the underside of the piston 74. These volumes are indicated by the presence of the small triangles.
- control port 72 is at atmospheric pressure and the atmospheric pressure is applied to the upper face of piston 74.
- the delivery ports 42 and 43 likewise are at atmospheric pressure as is the exhaust port at all times. Under these conditions there is zero pressure differential across the piston 74. Note that the area of the upper and lower faces of piston 74 is equal and that the piston 74 is sealed to the cylinder wall 73 by an O ring 75. The underside of the piston is maintained at atmospheric pressure during unoperated periods via ports 58 in the upper side wall of the spool 51.
- FIG. 3 shows the near 1:1 ratio of delivery pressure to application pressure over the range of zero to 100 psi on both increasing and decreasing pressure. There is extremely small hysteresis s illustrated by the area inside the two nearly straight lines of operations.
- the low opening pressure, low hysteresis and fast response of the relay and booster valves of this invention are achieved principally by reason of the balance of forces maintained across both the piston 74 and the spool 51 at all conditions.
- Balance across the piston 74 is facilitated since the top and bottom surface areas of the piston are equal in area and the piston is free to move until the forces across O ring 75 are balanced. All of the top surface of the piston is exposed to control pressure from port 72. In the normal non-operated condition this is atmosphere pressure over line 10 of FIG. 1.
- the under side of piston 74 is exposed to the exhaust port 45, also atmospheric pressure.
- the piston 74 forces are balanced and it will respond to any low operating pressure e.g. 1 psi at control outlet 72.
- the only force on the piston 74 is the return spring 53 until the piston 74 and spool 51 reaches the upper limit of travel and ports 58 are opened.
- the spool 51 is balanced with respect to the supply pressure at the closed position shown in FIG. 2 since the spool 51 and two O rings 55 and 56 present equal areas to the supply pressure through port 41.
- Supply pressure from port 41 exerts forces radially inward only on the body of the spool 51 and none tends to restrict either the opening or the closing of the spool 51 valve.
- Supply pressure at the level of the control pressure flows to the brakes through ports 42 and 43. Equilibrium or balancing of forces at any static position of piston 74 exists. As an example, where the supply pressure at port 41 is 100 psi and 1 psi (above atmosphere) is applied to the control port 72, approximately 5 lbs. gauge downward force (1 psi ⁇ 5 in. sq.) is applied to the upper surface of the piston 74. Atmospheric pressure of approximately 15 psi (0 gauge) opposes the movement of piston 74.
- the 1 psi is the pressure differential across O ring 75.
- supply pressure of 100 psi indicated in FIG. 2A by the line with superimposed + signs passes O ring 56 in the grooves 66 between lands 52A into the volume under the piston 74 and out through the delivery ports 42 and 43.
- downward force on the O ring 55 on the spool 51 remains 100 psi while the upper O ring 56 is relieved of pressure differential as the supply air fills the underside of the piston 74 and flows out through the delivery ports 42 and 43.
- a further objective of this invention is to provide a booster valve suitable for installation on a dolly having a pair of service brakes and a reservoir but no spring brake system.
- a booster valve suitable for installation on a dolly having a pair of service brakes and a reservoir but no spring brake system.
- control line 10 may be seen which is a continuation in actual operation of the control line 10 of FIG. 1.
- the dolly on which this system is mounted is secured by coupling 20 to the preceding section of control line
- the control line 10 is connected to the inlet port 72 of booster valve 80 of this invention and employs its delivery ports 42 and 43 for delivery of the control pressure to following dolly or trailers by control line 10A from port 42 and to the local relay emergency valve 90 from port 43 via control line 10B.
- the booster valve 80 passes control line pressure to an outlet coupling 20 at the end of control line 10A via shut off cock 17 normally in its open position similar to FIG. 1.
- Control line 10B provides the control pressure input to relay valve 90 which is preferably a Sealco Dolly Relay Emergency Valve No.
- Emergency supply port 91 is also coupled via lines 23 and 93 and a two way check valve 94 to reservoir 25.
- Supply port 41 is coupled via line 95 and pressure protection valve 96 to reservoir 25 as the supply to the reservoir 25.
- Pressure protection valve 96 may be a valve such as the Sealco Pressure Protection valve No. 110257.
- the two service delivery ports 100 and 101 of dolly relay emergency 90 serve two service brakes 34 via respective service brake lines 102 and 103.
- Their source of supply pressure is the reservoir 25 via line 97 port 92 of valve 90.
- FIG. 5 For a more complete understanding of the booster valve 80 and its operation, reference is now made to FIG. 5 in which, again, the same elements present in FIG. 2 are given the same reference numerals as in FIG. 2 and the same method of representing air flow is used except that delivery pressure exists at two different levels and are designated by a triangle for the lower flow rates and pressure and the diamond for the higher flow rates and pressure.
- the booster valve 80 is typically mounted to dolly 110 by a bracket 111 employing two of the assembly bolts 171 corresponding to bolt 71 of FIG. 2 but of greater length to accommodate the present of a separator plate 112 present between the valve body 40 and cover 70.
- the delivery ports 42 and 43 as well as the exhaust port 44 and its cover 45 are located in the bottom of the valve body 40 as is the perforated exhaust diaphram 46 and return spring 53 for the spool In this case the delivery port 42 and 43 will exhibit different flow rates and pressures which will be described below.
- the pressure at the port 43 will equal that present in that same port in the valve of FIG. 2 however, the flow rate will be modified by the presence of bypass check valve 113 present in the separator plate 112 and blocking the port 43 from the underside of the piston 74.
- the valve body 40 defines the same cylinder 52 and the spool 51 is sealed to cylinder wall 52 by O ring 55 at the bottom and O ring 56 at the top when the spool 51 is in its, at rest, position.
- the valve body 40 also includes the supply port 41. It can therefore be seen that the body 40 and its internal components are unchanged as compared with valve of FIG. 2.
- the cover 70 likewise is unchanged from the embodiment of FIG. 2 and the piston 74 is virtually unchanged with the exception that it lacks an O ring groove and O ring at the top of the axial column 78 and is longer to extend through the separator plate 112.
- the elements of the combination which change from the relay valve of FIG. 2 to the booster valve of FIG. 5 are located in the separator plate 112.
- First and most important component of the separator plate is its upper wall 114 which separates the volume below the piston 74 from the manifold region 115 which communicates with the delivery ports 42 and 43 as well as the supply port 41 when the booster valve is operated.
- the upper wall 114 of the separator plate 112 includes a plurality of openings 116 therethrough, which are located above a simple rubber check valve 120 in the form of a cup located on a pillar 121 which is integral with the valve body 40.
- check valve 120 When pressure in the manifold 115 below the upper wall 114 of the separator plate 112 is greater than that pressure below the piston 74, check valve 120 is closed. When the reverse situation exists, check valve allows pressure equalization between the two chambers with flow from the region below the piston 74 to the manifold region 115. Separator plate 112 is sealed to the piston 74 stem 78 by O ring 161.
- the separator plate 112 also mounts the bypass check valve 113 which blocks the upper entrance 143 to the delivery port 43.
- the bypass check valve 113 comprises a generally top hat shape plastic poppet 122 including a central orifice 123 and an outer rim 124 which seals against the seat 125 formed integrally in the valve body 40.
- a light spring 126 bearing against the under face of the upper wall 114 of the separator plate 112 holds the bypass check valve 113 in a closed position. Flow from the manifold 115 to the delivery port 43 is through the orifice 123. Whenever the reverse pressure differential exist between the delivery port 43 and the manifold 115 sufficient to compress spring 126, the bypass check valve opens and pressure is rapidly equalized between the port 43 and the manifold 115. This occurs upon brake release.
- the booster valve 80 of FIG. 5, was designed particularly to relay the signal on the control line in an air brake system of multiple unit tractor and trailers, i.e. double and triple trailers with a minimum of time delay in both operate and release cycle.
- the booster valve 80 exhibits the same low opening pressure, e.g. 1 psi on the control line 10 insuring that the control signal is picked up and relayed to the rear trailer at the lowest possible signal level.
- the balance of forces in the booster valve 80 on both the piston 74 and the spool 51 with virtually no hysteresis insures that the signal relayed to the rear trailer will not be at a lower pressure.
- the booster feature of the valve insures that the fastest possible signal is relayed to the rear trailer units by controlling the flow of delivery air pressure to the dolly port 42, the driver has the assurance that the dolly brakes 34 are not applied prior to the rear trailer brakes.
- valve 80 Similar to valve 40 of FIG. 2, occurs with supply air pressure furnished to port 41 and the supply air surrounds the spool 51 in the areas indicated by the +sign whenever the spool 51 has its retaining ring 60 bearing against captured washer 61. This is the normal, at rest, position for the spool 51 and it remains in this position unless a downward force from piston 74 moves spool 51.
- air pressure from control valve in the cab is introduced into port 72 filling the cavity between the cover 70 and the upper face of piston 74.
- the introduction of air pressure on top piston 74 moves the piston downward, hereby closing the first internal ports 58 thus closing communication between the manifold 115 and the exhaust port 44.
- the low opening feature of the valve 80 is achieved by the fact that pressure from the reservoir 25 arriving at port 41 working against both O rings 55 and 56 having the same effective area produces no biasing force in either direction.
- air pressure from the control valve in the cab via port 72 is introduced and into the valve 80 and moves piston 74 downward, the only opposing force is the spring 53 acting through spool 51.
- the balance of delivery pressure at port 43 and port 42 to the control line pressure of port 72 is achieved by the unique design of the spool assembly. Delivery pressure under the piston 74 is applied to the underside of O ring 75, to the underside of O ring 67, the topside of O ring 161 and to the underside of O ring 68.
- FIG. 7 illustrates the operating characteristics of a conventional brake system including a tractor, a lead trailer, a dolly and a rear trailer with the x axis representing pressure at 20 psi per division and the y axis measuring time in seconds from the instant of brake pressure application.
- the application time for pressure to rise from 0 psi to 60 psi is marked by a cross. This is the time from the driver's application of his foot to the brake pedal in the wide open brake application to the time each axle actually receives 60 psi of air pressure.
- FIG. 7 illustrates a typical air brakes system as used throughout the United States today.
- the timing from 0 to 60 psi on the tractor axle is 0.216 seconds shown on the bottom curve.
- the lead trailer reaches 60 psi in 0.787 seconds.
- the dolly axle reaches 60 psi in 0.863 seconds.
- the rear most trailer axle reaches 60 psi in 0.993 seconds.
- FIG. 8 exactly the same system as used in obtaining the curve of FIG. 7, except for the addition of the booster valve of FIG. 5 is now illustrated.
- the improvement may be seen.
- the lower wave form for the tractor shows an operate time, of 0.219 seconds, virtually the same as in the previous system.
- the lead trailer has an operate time of 0.537 seconds, an improvement of 32%.
- the dolly axle applies 60 psi in 0.583 seconds, also a 32% improvement.
- the rear axle brakes reach 60 psi in 0.993 seconds, again for a 32% improvement.
- the overall system improvement for all towed trailer is 32%. This coupled with the low opening or operating pressure highlights the importance of this invention.
- the curves in this figure illustrate the same brake system as present in FIG. 7 in which the release of air from the brake system is timed from 95 psi to the air brake chamber at the axle down to 5 psi in each axle.
- the lower curve shows the tractor pressure, the next curve the lead trailer, the third curve, the dolly and the fourth curve, the rear trailer.
- the release time for the tractor is 1.204 sec.
- the lead trailer is 1.429 sec.
- the dolly is 1.486 sec.
- the rear trailer is 1.802 sec.
- the operating characteristic is then illustrated in FIG. 10 with the curves in the same order.
- the tractor release time is 1.183 sec., the lead trailer 1.422 sec., the dolly 1.422 sec. and the rear trailer 1.448 sec. In each case the release time is improved and particularly the rear trailer illustrates the most improvement.
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- Valves And Accessory Devices For Braking Systems (AREA)
Abstract
Description
______________________________________ O Ring No. Area Sealed in sq. in. ______________________________________ 84 0.4418 67 1.1075 68 0.3712 75 9.6211 56 0.866 55 0.886 ______________________________________
Claims (21)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US07/058,406 US4856851A (en) | 1987-06-05 | 1987-06-05 | Relay and booster valves for air brake systems |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US07/058,406 US4856851A (en) | 1987-06-05 | 1987-06-05 | Relay and booster valves for air brake systems |
Publications (1)
Publication Number | Publication Date |
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US4856851A true US4856851A (en) | 1989-08-15 |
Family
ID=22016620
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US07/058,406 Expired - Lifetime US4856851A (en) | 1987-06-05 | 1987-06-05 | Relay and booster valves for air brake systems |
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Country | Link |
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US (1) | US4856851A (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5131694A (en) * | 1991-02-26 | 1992-07-21 | Midland Manufacturing Corp. | Joint seal between valve body and removable port |
US20100243929A1 (en) * | 2009-03-30 | 2010-09-30 | Flavio Tondolo | Booster valve |
US20140026746A1 (en) * | 2010-09-15 | 2014-01-30 | Fisher Controls International Llc | Volume booster with stabilized trim |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3411836A (en) * | 1967-08-23 | 1968-11-19 | Berg Mfg & Sales Co | Relay emergency modulating valve |
US4078844A (en) * | 1976-11-29 | 1978-03-14 | Clayton Dewandre Company Limited | Truck and trailer braking systems |
-
1987
- 1987-06-05 US US07/058,406 patent/US4856851A/en not_active Expired - Lifetime
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3411836A (en) * | 1967-08-23 | 1968-11-19 | Berg Mfg & Sales Co | Relay emergency modulating valve |
US4078844A (en) * | 1976-11-29 | 1978-03-14 | Clayton Dewandre Company Limited | Truck and trailer braking systems |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5131694A (en) * | 1991-02-26 | 1992-07-21 | Midland Manufacturing Corp. | Joint seal between valve body and removable port |
US20100243929A1 (en) * | 2009-03-30 | 2010-09-30 | Flavio Tondolo | Booster valve |
US8522818B2 (en) * | 2009-03-30 | 2013-09-03 | Sti Srl | Booster valve |
US20140026746A1 (en) * | 2010-09-15 | 2014-01-30 | Fisher Controls International Llc | Volume booster with stabilized trim |
US9677578B2 (en) * | 2010-09-15 | 2017-06-13 | Fisher Controls International Llc | Volume booster with stabilized trim |
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